From 155d84c555d65803dad8d96969b5d5481aa8d9c6 Mon Sep 17 00:00:00 2001
From: Alban Crequy <albancrequy@linux.microsoft.com>
Date: Wed, 24 May 2023 20:21:44 +0200
Subject: [PATCH] New functions GetFrom{Pid,Thread}WithAltProcfs

Existing functions GetFrom{Pid,Thread}() need the pid/tid argument to
be numbered as per the pid namespace of the /proc mount.

In some container configurations, this is not suitable: a container with
unshared pid namespace and the host's /proc mounted in /host/proc needs
to lookup pids numbered as per the host pid namespace in /host/proc.

GetFrom{Pid,Thread}WithAltProcfs() provide a way for such container
setups to use an alternative /proc path.
---
 netns_linux.go  | 12 ++++++++++++
 netns_others.go |  8 ++++++++
 2 files changed, 20 insertions(+)

diff --git a/netns_linux.go b/netns_linux.go
index 8c9b177..a18b89b 100644
--- a/netns_linux.go
+++ b/netns_linux.go
@@ -122,6 +122,18 @@ func GetFromThread(pid, tid int) (NsHandle, error) {
 	return GetFromPath(fmt.Sprintf("/proc/%d/task/%d/ns/net", pid, tid))
 }
 
+// GetFromPidWithAltProcfs gets a handle to the network namespace of a given
+// pid using the specified procfs path.
+func GetFromPidWithAltProcfs(pid int, procfs string) (NsHandle, error) {
+	return GetFromPath(fmt.Sprintf("%s/%d/ns/net", procfs, pid))
+}
+
+// GetFromThreadWithAltProcfs gets a handle to the network namespace of a given
+// pid and tid using the specified procfs path.
+func GetFromThreadWithAltProcfs(pid, tid int, procfs string) (NsHandle, error) {
+	return GetFromPath(fmt.Sprintf("%s/%d/task/%d/ns/net", procfs, pid, tid))
+}
+
 // GetFromDocker gets a handle to the network namespace of a docker container.
 // Id is prefixed matched against the running docker containers, so a short
 // identifier can be used as long as it isn't ambiguous.
diff --git a/netns_others.go b/netns_others.go
index f444f6e..00c205e 100644
--- a/netns_others.go
+++ b/netns_others.go
@@ -51,6 +51,14 @@ func GetFromThread(pid int, tid int) (NsHandle, error) {
 	return -1, ErrNotImplemented
 }
 
+func GetFromPidWithAltProcfs(pid int, procfs string) (NsHandle, error) {
+	return -1, ErrNotImplemented
+}
+
+func GetFromThreadWithAltProcfs(pid, tid int, procfs string) (NsHandle, error) {
+	return -1, ErrNotImplemented
+}
+
 func GetFromDocker(id string) (NsHandle, error) {
 	return -1, ErrNotImplemented
 }